1. Field of the Invention
The present invention relates to a display including a self-luminous type light-emitting element which includes an organic layer, and a method of manufacturing the same.
2. Description of the Related Art
In recent years, as displays replacing liquid crystal displays, organic EL (Electro Luminescence) displays using a self-luminous type organic EL element which includes an organic layer have been put into practical use. The organic EL display are of a self-luminous type, so compared to liquid crystal displays, the organic EL displays have a wide viewing angle, and adequate response to high-definition high-speed video signals.
A resonator configuration is introduced into an organic EL element in related art, thereby an attempt to improve display performance has been made by controlling light generated in a light-emitting layer such as improving color purity of an emitted color or improving light emission efficiency as described in, for example, International Publication No. 01/39554. For example, in a top emission system in which light is extracted from a surface (a top surface) opposite to a substrate, an anode electrode, an organic layer and a cathode electrode are laminated in order on the substrate with a driving transistor in between, and light from the organic layer is multiply reflected between the anode electrode and the cathode electrode.
In a top emission system organic EL display, to secure a high aperture ratio, a cathode electrode located on a sealing panel side is one electrode layer commonly arranged for organic EL elements. Moreover, the cathode electrode is made of, for example, a light transmissive conductive material such as ITO (Indium Tin Oxide) so as to extract light from a top surface. However, such a light transmissive conductive material has a few orders of magnitude higher resistance than a typically used metal material. Therefore, a voltage applied to the cathode electrode easily becomes nonuniform in a plane, so there is an issue that variations in light emission luminance among organic EL elements in an in-plane position occur, thereby it is difficult to obtain sufficient display quality.
Therefore, to solve such an issue, for example, as described in Japanese Unexamined Patent Application Publication No. 2004-207217, there is proposed an organic EL display in which an auxiliary wire connected to the cathode electrode is formed of a layer shared with, for example, the anode electrode located on a drive panel side so as to prevent a voltage drop in an in-plane direction of the cathode electrode. The auxiliary wire is connected to the cathode electrode, for example, outside a display region of each organic EL element. Thus, the auxiliary wire is arranged in a mesh form along the cathode electrode spreading in an in-plane direction, and is connected to the cathode electrode, thereby variations in light emission luminance among organic EL elements in the above-described in-plane position are reduced to some extent.
In the case where the organic EL display having the above-described auxiliary wire is formed, to simplify manufacturing steps, for example, it is desirable to collectively form the anode electrode and the auxiliary wire using a common material. As a material of the anode electrode, a simple substance or a compound of aluminum having high reflectivity is most preferable. However, in the case where such a material is used to form an auxiliary electrode, oxidation of a surface of the auxiliary electrode during the manufacturing steps is an issue. More specifically, when the surface of the auxiliary electrode is oxidized, connection resistance between the auxiliary electrode and the cathode electrode is increased, thereby to cause a large voltage drop in a connection part between the auxiliary electrode and the cathode electrode. Therefore, nonuniformity of a light emission luminance distribution in a display screen may not be reduced sufficiently.
To solve such an issue, for example, as described in International Publication No. 2007/148540, the applicant of the present invention has proposed an organic EL display in which a conductive contact section is formed in advance, and then an anode electrode and an auxiliary wire, and a cathode electrode are formed in order so as to be in contact with the contact section.